1. Field of the Invention
The present invention relates to waveform display equipment which displays a plurality of waveforms based on the waveform data obtained by measuring signals to be measured in the display region of a display screen and a waveform displaying method to display such waveforms. Specifically, the invention relates to waveform display equipment and a waveform displaying method, in which a plurality of waveforms is easily observed and measured.
2. Description of the Prior Art
A waveform measuring system measures various physical quantities such as temperature, pressure, strain resistance, etc. by converting those quantities to electrical signals using converting means suitable for each application, and stores them as waveform data. In such a system, variations of these electrical signals, that is, variations of the physical quantities, can be observed and measured by displaying waveforms in the display region of a display screen based on the stored waveform data. Electrical signals such as input/output signals to/from electrical circuits can, of course, also be displayed. Such a system includes paperless recorders, digital oscilloscopes, etc.
Waveform display equipment used for the waveform measuring system can simultaneously display a plurality of waveforms, for example, taking voltage values as the ordinate and time as the abscissa (for instance, refer to the gazette of Japanese Laid-open Patent Application No. 8-29455).
However, if various physical quantities are to be measured, it is necessary to carry out measurement using optimum measuring periods respectively. For example, a signal whose changes are slow such as temperature signals needs to be measured using a slow measuring period (e.g., 1-s interval), and a signal whose changes are fast such as input/output signals to/from electric circuits must be measured using a fast measuring period (e.g., 10-ms interval).
FIG. 1 shows an example of displaying waveform data obtained by measurement using different measuring periods. In FIG. 1, waveform 100 shows a waveform obtained by measurement using a fast measuring period (for example, 10 ms) and waveform 101 shows a waveform obtained by measurement using a slow measuring period (for example, 1 s). FIG. 1(a) is an example of a display suitable for a fast measuring period and FIG. 1(b) is an example of a display suitable for a slow measuring period.
FIG. 1(a) displays waveform 100 by setting the abscissa so that waveform 100 can be conveniently observed. However, waveform 101 is shown rather flat due to this setting and thus its observation and measurement become difficult. On the other hand, FIG. 1(b) displays waveform 101 by setting the abscissa so that waveform 101 can be conveniently observed. However, due to this setting, waveform 100 is displayed rather overlapping the time base and so its observation and measurement become difficult. That is, these waveform measuring systems in the prior art have a problem that, if signals whose varying conditions are different with time respectively are to be observed and measured, it is hard to obtain a display that is optimum for all signal waveforms 100, 101, etc.